Humans will consume the whitetip reef shark; in particular they use the fins in soup.
Positive Impacts: food
The most dangerous predator of the whitetip reef shark is humans. However, in the ocean they can be prey for large carcharhinid sharks, such as the tiger shark (Galeocerdo cuvier) or the silvertip shark (Carcharhinus albimarginatus).
Known Predators:
The whitetip reef shark is a medium-sized shark averaging about 1.6 meters in length and 20 kg in mass, but growing as big as 2 meters and 28 kg. It is grey in color with a white belly and characteristic white tips on its first dorsal, upper caudal and occasionally the pelvic fins. The snout is short and broad with a mouth full of smooth edged teeth on both jaws. Both the mouth and nostrils are located on the underside of the head. The skin is very tough and the lateral fins are highly flexible. Both of these characteristics allow them to exist more easily among the rough and jagged edges of a coral reef. A diagnostic feature that distinguishes Carcharhinus albimarginatus from the similar silvertip and oceanic whitetip sharks is the second dorsal fin. In the whitetip reef shark it is significantly larger in comparison to the other species.
Range mass: 27.7 (high) kg.
Average mass: 20 kg.
Range length: 213 (high) cm.
Average length: 165 cm.
Other Physical Features: ectothermic ; bilateral symmetry
Sexual Dimorphism: male larger
The whitetip reef shark is believed to live to a maximum of 25 years.
Range lifespan
Status: wild: 25 (high) years.
Average lifespan
Status: captivity: 25 years.
Carcharhinus albimarginatus is a reef shark as its name would indicate and lives in or around coral reefs. These reef settings are in tropical, coastal waters. Being a nocturnal animal, it spends much of the day in caves and deep crevices in coral reefs or coral reef lagoons. Whitetip reef sharks share these habitats with other reef sharks. However each species takes on a particular location within the reef system. The blacktip reef shark takes the shallow, high-energy coastal waters. The grey reef shark takes the deeper clear waters off the reef edge. The whitetip reef shark is the shark that lives in among the coral reefs, most commonly between the depths of 8 and 40 meters.
Range depth: 1 to 330 m.
Average depth: 8-40 m.
Habitat Regions: tropical ; saltwater or marine
Aquatic Biomes: benthic ; reef ; coastal
Other Habitat Features: caves
The whitetip reef shark in found in both the Indian and Pacific oceans. They exist as far west as the coasts of South Africa and Sri Lanka in the Indian Ocean and can be seen as far east as the coasts of Costa Rica and Panama in the Pacific Ocean. They are most prominent in the Indo-Pacific seas and around the southern coast of the Indian sub-continent. Fossils have been found in North Carolina from the Miocene epoch indicating that the shark existed in the Atlantic Ocean several million years ago; however they not currently found in the Atlantic Ocean.
Biogeographic Regions: oriental (Native ); indian ocean (Native ); pacific ocean (Native )
Despite the docile nature of this shark during the day, during feeding at night they become very aggressive. It will thrash through coral reefs looking for food. The whitetip reef shark usually hunts alone but will work with other sharks to pursue prey throughout the coral reefs. Sometimes in pursuit of a fish, the shark will wedge the front half of its body into a crack or crevice on the reef and stay there until it catches the fish. The whitetip reef shark is considered clumsy and slow in open water, however it is still considered a pelagic predator. It is capable of catching fish in coral reefs because of its maneuverability. Despite its ability to catch fish, it specializes in bottom feeding. Its ventrally located mouth is ideal for picking crab, lobster and octopi off the sea floor, but its primary source of food is several types of boney fishes including but not restricted to damselfish (Pomacentridae), parrotfish (Scaridae), surgeonfish (Acanthuridae), goatfish (Mullidae), triggerfish (Balistidae), squirrelfish (Holocentridae) and eels (Anguilliformes).
Animal Foods: fish; aquatic crustaceans
Primary Diet: carnivore (Piscivore )
The whitetip reef shark uses the coral reefs as a habitat, as well as a source for food. They are important predators in reef ecosystems. The sharks’ predation of fishes may serve as a sort of population control. This is particularly important in those fishes, such as the parrotfish, that consume the coral.
However the whitetip reef shark does occasionally have a negative effect on the coral. These sharks sometimes damage corals in their aggressive pursuit of prey fish.
The whitetip reef shark also serves as host to small cleaner fish such as gobies or striped cleaner wrasses who feed on the parasites infesting the shark.
Mutualist Species:
The whitetip reef shark is only a problem to humans if provoked. They are considered to be a passive, calm animal that is easily approachable by divers. A whitetip reef shark will also attack in defense if escape is not an option. Altercations with spear fisherman can occur; most commonly in dispute over possession of the speared fish. It is thought that the sound of spear fishing arouses the shark, and therefore results in their abandonment of the cave and eventual pursuit of the speared fish.
Although the flesh of these sharks is sometimes eaten for food, there are reports that the tissues, particularly the liver, may be toxic.
Negative Impacts: injures humans (bites or stings, poisonous )
The embryos are maintained in the mother for 5 months. They are then born alive and fully functional. The new-born juveniles are a mini-version of an adult whitetip reef shark, capable of surviving on their own. They grow relatively slowly however, and reach sexual maturity five years later.
There are no special conservation projects involving the whitetip reef shark. It currently has a wide tropical distribution. However, it's slow rate of reproduction would make it very vulnerable to over-fishing. The IUCN rates the species "Lower Risk/Not Threatened."
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: near threatened
As with most sharks the main form of perception is visual. Sharks in general tend to have good eyesight especially in dim light. The eyes are large and oval in shape. The large eyes are particularly useful to the whitetip because it is a nocturnal animal that does most of its hunting and traveling at night.
Like other sharks, they have very strong chemosensory systems as well. This is most useful to the whitetip reef sharks in hunting and eating.
Whitetip reef sharks respond to sounds in the water. They are believed to be attracted to the sounds of spearfishing in the water.
Like other sharks, this species also has electroreceptive abilities to help them detect prey.
Very little is known about the communication of these sharks with each other. It is known that they do share caves, and occasionally hunt together, however the way in which they communicate isn’t fully understood. One case in which the communication is obvious is in mating where there is a clear tactile communication in the act of the male biting the fins of the female.
Communication Channels: visual ; tactile ; chemical
Perception Channels: visual ; tactile ; acoustic ; chemical ; electric
This species was originally described by Eduard Ruppell in 1837.
Male whitetip reef sharks have been known to school in groups of nearly a hundred in pursuit of a female ready to mate. Mating in this particular species happens in autumn and winter. The sharks orient themselves parallel to each other and at about a 45 degree angle to the water column during copulation. They position themselves with their snouts in the sea floor, maintaining this vertical position with occasional simultaneous undulations of their bodies. The male then bites the pectoral fin of the female and inserts his clasper into the cloaca. This ritual of biting the female’s pectoral fin to hold position is common to several species.
Once the female is pregnant, the gestation period is thought to be about 5 months, however more research is needed in this area. The female gives birth to 2 or 3 live sharks of about 60 cm each.
Breeding interval: There is not sufficient evidence to indicate how often this species breeds.
Breeding season: Fertilization occurs seasonally in autumn and winter. This is between May and August in the Southern Hemisphere.
Range number of offspring: 1 to 5.
Average number of offspring: 2-3.
Average gestation period: 5 months.
Average age at sexual or reproductive maturity (female): 5 years.
Average age at sexual or reproductive maturity (male): 5 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); viviparous
Average age at sexual or reproductive maturity (female)
Sex: female: 2920 days.
Because the whitetip reef shark is a viviparous species it gives birth to live young. While in the embryo stage, the juvenile receives all its nutrients from the mother via a yolk sac placenta. The female shark, having a litter of young sharks within her, is slower and less maneuverable making her more vulnerable to predators. All of the parental investment in this species is by the female, and it is all internal in embryo stage. Once the juveniles are born, they are completely independent and capable of fending for themselves.
Parental Investment: female parental care ; pre-hatching/birth (Provisioning: Female, Protecting: Female)
The whitetip reef shark (Triaenodon obesus) is a species of requiem shark, in the family Carcharhinidae, and the only member of its genus. A small shark that does not usually exceed 1.6 m (5.2 ft) in length, this species is easily recognizable by its slender body and short but broad head, as well as tubular skin flaps beside the nostrils, oval eyes with vertical pupils, and white-tipped dorsal and caudal fins. One of the most common sharks found on Indo-Pacific coral reefs, the whitetip reef shark occurs as far west as South Africa and as far east as Central America. It is typically found on or near the bottom in clear water, at a depth of 8–40 m (26–131 ft).
During the day, whitetip reef sharks spend much of their time resting inside caves. Unlike other requiem sharks, which rely on ram ventilation and must constantly swim to breathe, this shark can pump water over its gills and lie still on the bottom. At night, whitetip reef sharks emerge to hunt bony fishes, crustaceans, and octopus in groups, their elongate bodies allowing them to force their way into crevices and holes to extract hidden prey. Individuals may stay within a particular area of the reef for months or years, frequently returning to the same shelter. This species is viviparous, in which the developing embryos are sustained by a placental connection to their mother.
Whitetip reef sharks are rarely aggressive towards humans, though they may investigate swimmers closely. However, spear fishers are at risk of being bitten by one attempting to steal their catch. This species is caught for food, though ciguatera poisoning resulting from its consumption has been reported. The IUCN has assessed the whitetip reef shark as Vulnerable, noting its numbers are dwindling due to increasing levels of unregulated fishing activity across its range. The slow reproductive rate and limited habitat preferences of this species renders its populations vulnerable to overfishing.
The whitetip reef shark was first described by the German naturalist Eduard Rüppell as Carcharias obesus, in the 1837 Fische des Rothen Meere (Fishes of the Red Sea).[2] His choice of the specific epithet obesus was curious, given that this shark is actually quite slender.[3] Later in 1837, Johannes Müller and Friedrich Henle moved this species into its own genus Triaenodon, from the Greek triaena meaning "trident", and odon meaning "tooth". As Rüppell did not originally designate a holotype, in 1960 a 31-cm-long specimen caught off Jeddah, Saudi Arabia, was made the species lectotype.[2] Other common names for this shark include blunthead shark, light-tip shark, reef whitetip shark, and whitetip shark.[4]
Once placed in the family Triakidae, the whitetip reef shark is now recognized by most authors as belonging to the family Carcharhinidae on the basis of morphological characters, such as a full nictitating membrane, well-developed precaudal pit, strong lower caudal fin lobe, and scroll-like intestinal valves.[5] Morphological and molecular phylogenetic analyses suggest the whitetip reef shark is grouped with the lemon sharks (Negaprion) and the sliteye shark (Loxodon) in occupying an intermediate position on the carcharhinid evolutionary tree, between most basal genera (Galeocerdo, Rhizoprionodon, and Scoliodon) and the most derived (Carcharhinus and Sphyrna).[6]
The whitetip reef shark is distributed widely across the entire Indo-Pacific region. It was once thought to have formerly existed in the Atlantic Ocean, based on fossil teeth found in North Carolina dating to the Miocene epoch. However, more recent research indicates that the teeth belonged to a mackerel shark, and that this species has never colonized the Atlantic.[7] In the Indian Ocean, it occurs from northern KwaZulu-Natal, South Africa to the Red Sea and the Indian subcontinent, including Madagascar, Mauritius, the Comoros, the Aldabra Group, the Seychelles, Sri Lanka, and the Chagos Archipelago. In the western and central Pacific, it occurs from off southern China, Taiwan, and the Ryukyu Islands, to the Philippines, Southeast Asia, and Indonesia, to northern Australia, and is also found around numerous islands in Melanesia, Micronesia, and Polynesia, as far as Hawaii to the north and the Pitcairn Islands to the southeast. In the eastern Pacific, it occurs from Costa Rica to Panama, and off the Galápagos Islands.[2]
Associated almost exclusively with coral reef habitats, whitetip reef sharks are most often encountered around coral heads and ledges with high vertical relief, and additionally over sandy flats, in lagoons, and near drop-offs to deeper water.[8] They prefer very clear water and rarely swim far from the bottom.[5] This species is most common at a depth of 8–40 m (26–131 ft).[2] On occasion, they may enter water less than 1 m deep, and there is an exceptional record of a whitetip reef shark being captured from a depth of 330 m (1,080 ft) in the Ryukyu Islands.[5]
A relatively small species, few whitetip reef sharks are longer than 1.6 m (5.2 ft). The maximum length this species attains is often given as 2.1 m (6.9 ft), though this was originally based on visual observations and may be dubious.[5] The maximum reported weight is 18.3 kg (40 lb).[4] The whitetip reef shark has a slim body and a short, broad head. The snout is flattened and blunt, with large flaps of skin in front of the nares that are furled into tubes. The eyes are small and oval with vertical pupils and prominent ridges above, and are often followed by a small notch. The mouth has a distinct downward slant (imparting a disgruntled expression to the shark), with short furrows at the corners. There are 42–50 tooth rows in the upper jaw and 42–48 tooth rows in the lower jaw. Each tooth has a single narrow, smooth-edged cusp at the center, flanked by a pair of much smaller cusplets.[2]
The first dorsal fin is positioned well back on the body, closer to the pelvic than the pectoral fins. The second dorsal and anal fins are large, about half to three-quarters as high as the first dorsal fin. The broad, triangular pectoral fins originate at or slightly before the level of the fifth gill slit. There is no ridge between the first and second dorsal fins. The lower lobe of the caudal fin is half the length of the upper, which has a strong notch near the tip.[2] The dermal denticles are small and overlapping, usually with 7 horizontal ridges, giving the skin a smooth feel. The coloration is grayish to brownish above and white below, with a pattern of scattered small, dark spots unique to each individual. The tips of the first dorsal fin and upper caudal fin lobe, and sometimes also the second dorsal fin and lower caudal fin lobe, are bright white.[5]
The whitetip reef shark is one of the three most common sharks inhabiting the reefs of the Indo-Pacific, the other two being the blacktip reef shark (Carcharhinus melanopterus) and the grey reef shark (Carcharhinus amblyrhynchos). The habitat preferences of this species overlap those of the other two, though it does not tend to frequent very shallow water like the blacktip reef shark, nor the outer reef like the grey reef shark.[2] The whitetip reef shark swims with strong undulations of its body, and unlike other requiem sharks can lie motionless on the bottom and actively pump water over its gills for respiration.[2] This species is most active at night or during slack tide, and spends much of the day resting inside caves singly or in small groups, arranged in parallel or stacked atop one another. Off Hawaii, these sharks may be found sheltering inside underwater lava tubes, while off Costa Rica they are often seen lying in the open on sandy flats.[9]
Whitetip reef sharks generally remain within a highly localized area; only rarely do they undertake long movements, wandering for a while before settling down somewhere new. One study at Johnston Atoll found that none of the sharks examined had moved more than 3 km (1.9 mi) away from their original capture location over periods of up to a year.[5] Another study at Rangiroa Atoll in French Polynesia found that, after more than three years, around 40% of the originally tagged sharks were still present on the same reef where they were first captured. An individual shark may rest inside the same cave for months to years. The daytime home range of a whitetip reef shark is limited to approximately 0.05 km2 (0.019 sq mi); at night this range increases to 1 km2 (0.39 sq mi).[9] These sharks are not territorial and share their home ranges with others of their species; they do not perform threat displays.[2][8]
Important predators of the whitetip reef shark include tiger sharks (Galeocerdo cuvier), Galapagos sharks (Carcharhinus galapagensis), and possibly also silvertip sharks (Carcharhinus albimarginatus), though they usually occur at depths greater than those favored by whitetip reef sharks. An 80 cm (31 in) long whitetip reef shark has also been found in the stomach of a giant grouper (Epinephelus lanceolatus), though these groupers are unlikely to be significant predators of this species due to their rarity.[5] Known parasites of the whitetip reef shark include the copepod Paralebion elongatus and the praniza (parasitic) larvae of the isopod Gnathia grandilaris.[10][11] While resting during the day, these sharks have been observed being cleaned by the wrasse Bodianus diplotaenia and the goby Elacatinus puncticulatus. Unusually, there is also a report of seven whitetip reef sharks adopting a cleaning posture (mouth agape and gills flared) in the midst of a swarm of non-cleaning hyperiid amphipods; the mechanical stimulation from the moving amphipods are thought to have evoked this behavior through their similarity to actual cleaner organisms.[12]
With its slender, lithe body, the whitetip reef shark specializes in wriggling into narrow crevices and holes in the reef and extracting prey inaccessible to other reef sharks. Alternatively, it is rather clumsy when attempting to take food suspended in open water.[5] This species feeds mainly on bony fishes, including eels, squirrelfishes, snappers, damselfishes, parrotfishes, surgeonfishes, triggerfishes and goatfishes, as well as octopuses, spiny lobsters, and crabs.[2] The whitetip reef shark is highly responsive to the olfactory, acoustic, and electrical cues given off by potential prey, while its visual system is attuned more to movement and/or contrast than to object details.[8][13][14] It is especially sensitive to natural and artificial low-frequency sounds in the 25–100 Hz range, which evoke struggling fish.[9]
Whitetip reef sharks hunt primarily at night, when many fishes are asleep and easily taken. After dusk, groups of sharks methodically scour the reef, often breaking off pieces of coral in their vigorous pursuit of prey.[15] Multiple sharks may target the same prey item, covering every exit route from a particular coral head. Each shark hunts for itself and in competition with the others in its group.[8] Unlike blacktip reef sharks and grey reef sharks, whitetip reef sharks do not become more excited when feeding in groups and are unlikely to be stirred into a feeding frenzy.[8] Despite their nocturnal habits, whitetip reef sharks will hunt opportunistically in daytime.[5] Off Borneo, this species gathers around reef drop-offs to feed on food brought up by the rising current.[16] Off Hawaii, they follow Hawaiian monk seals (Monachus schauinslandi) and attempt to steal their catches.[6] A whitetip reef shark can survive for six weeks without food.[5]
Like other members of its family, the whitetip reef shark is viviparous; once the developing embryos exhaust their supply of yolk, the yolk sac is converted into a placental connection through which the mother delivers nourishment for the remainder of gestation. Mature females have a single functional ovary, on the left side, and two functional uteruses. The reproductive cycle is biennial.[17]
Mating is initiated when up to five males follow closely behind a female and bite at her fins and body, possibly cued by pheromones indicating the female's readiness.[18] Each male attempts to seize the female by engulfing one of her pectoral fins; at times two males might grasp a female on both sides simultaneously. Once engaged, the sharks sink to the bottom, whereupon the male (or males) rotates one of his claspers forward, inflates the associated siphon sac (a subcutaneous abdominal organ that takes in seawater that is used to flush sperm into the female), and attempts to make contact with the female's vent. In many cases, the female resists by pressing her belly against the bottom and arching her tail; this may reflect mate choice on her part. The male has a limited time in which to achieve copulation, as while he is holding the female's pectoral fin in his mouth he is being deprived of oxygen. On the other hand, if the female is willing, the pair settles side-by-side with their heads pressed against the bottom and their bodies at an upward angle.[19][20]
After a gestation period of 10–13 months, females give birth to litters of 1–6 (usually 2–3) pups. The number of offspring is not correlated with female size; each female produces an estimated average of 12 pups over her entire lifetime.[17] Parturition occurs from May to August (autumn and winter) in French Polynesia, in July (summer) off Enewetak Atoll, and in October (summer) off Australia.[2][17] Females give birth while swimming, making violent twists and turns of their bodies; each pup takes under an hour to fully emerge.[21] The newborns measure 52–60 cm (20–24 in) long and have relatively longer caudal fins than adults. This shark develops slowly compared to other requiem sharks; newborns grow at a rate of 16 cm (6.3 in) per year while adults grow as a rate of 2–4 cm (0.79–1.57 in) per year.[5] Sexual maturity is reached at a length of around 1.1 m (3.6 ft) and an age of 8–9 years, though mature males as small as 95 cm (37 in) long have been recorded from the Maldives, suggesting regional variation in maturation size.[22] On the Great Barrier Reef, males live to 14 years and females to 19 years; the maximum lifespan of this shark may be upwards of 25 years.[5][17] In 2008, a whitetip reef shark produced a single pup through possibly asexual means at the Nyiregyhaza Centre in Hungary; previous instances of asexual reproduction in sharks have been reported in the bonnethead (Sphyrna tiburo) and the blacktip shark (Carcharhinus limbatus).[23]
Unlike its Oceanic cousin, the white tip reef shark is more harmless and is seldom aggressive unless provoked. They are also fearless and curious, as the whitetip reef sharks may approach swimmers closely to investigate. However, these sharks readily attempt, and quite boldly, to steal catches from spear fishers, which has resulted in several people being bitten in the process.[5] In some places, local whitetip reef sharks have learned to associate the sound of a speargun discharge or a boat dropping anchor with food and respond within seconds.[9] As of 2008, the International Shark Attack File lists two provoked and three unprovoked attacks to this species.[24] Whitetip reef sharks are well-suited to ecotourism diving, and with conditioning they can be hand-fed by divers.[2] In Hawaiian mythology, the fidelity (i.e. "loyalty") of whitetip reef sharks to certain areas of the reef for years at a time may have inspired belief in ʻaumākua, the spirits of family ancestors that take animal form and protect their descendants.[25]
The whitetip reef shark is taken by fisheries operating off Pakistan, India, Sri Lanka, Madagascar, and likely elsewhere, using longlines, gillnets, and trawls. The meat and liver are eaten, though sharks from certain areas present a substantial risk of ciguatera poisoning (especially the liver, which contains a much higher concentration of the toxin than the meat).[2][5] The International Union for Conservation of Nature (IUCN) has assessed this species as Vulnerable, as its numbers have dropped in recent decades due to increasing, and thus far unregulated, fishing pressure in the tropics.[22] Its restricted habitat, low dispersal, and slow reproduction are factors that limit this shark's capacity for recovering from overfishing.[1] On the Great Barrier Reef, populations of whitetip reef sharks in fishing zones have been reduced by 80% relative to no-entry zones. Furthermore, populations in no-take zones, where boats are allowed but fishing prohibited, exhibit levels of depletion comparable to fishing zones due to poaching. Demographic models indicate that these depleted populations will continue to decline by 6.6–8.3% per year without additional conservation measures.[17] In June 2018 the New Zealand Department of Conservation classified the whitetip reef shark as "Vagrant" under the New Zealand Threat Classification System.[26]
The whitetip reef shark (Triaenodon obesus) is a species of requiem shark, in the family Carcharhinidae, and the only member of its genus. A small shark that does not usually exceed 1.6 m (5.2 ft) in length, this species is easily recognizable by its slender body and short but broad head, as well as tubular skin flaps beside the nostrils, oval eyes with vertical pupils, and white-tipped dorsal and caudal fins. One of the most common sharks found on Indo-Pacific coral reefs, the whitetip reef shark occurs as far west as South Africa and as far east as Central America. It is typically found on or near the bottom in clear water, at a depth of 8–40 m (26–131 ft).
During the day, whitetip reef sharks spend much of their time resting inside caves. Unlike other requiem sharks, which rely on ram ventilation and must constantly swim to breathe, this shark can pump water over its gills and lie still on the bottom. At night, whitetip reef sharks emerge to hunt bony fishes, crustaceans, and octopus in groups, their elongate bodies allowing them to force their way into crevices and holes to extract hidden prey. Individuals may stay within a particular area of the reef for months or years, frequently returning to the same shelter. This species is viviparous, in which the developing embryos are sustained by a placental connection to their mother.
Whitetip reef sharks are rarely aggressive towards humans, though they may investigate swimmers closely. However, spear fishers are at risk of being bitten by one attempting to steal their catch. This species is caught for food, though ciguatera poisoning resulting from its consumption has been reported. The IUCN has assessed the whitetip reef shark as Vulnerable, noting its numbers are dwindling due to increasing levels of unregulated fishing activity across its range. The slow reproductive rate and limited habitat preferences of this species renders its populations vulnerable to overfishing.
